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CHAPTER 41: GLOMERULAR FILTRATION (Physiology of kidney (Nephron ([in] =…
CHAPTER 41: GLOMERULAR FILTRATION
Physiology of kidney
functions:
filter blood
excrete metabolic waste
retrieve filtered sub. needed by body
produce hormone; regulate BP & RBC production
respond to: h2o, electrolyte & acid-base disturbances
nephron → collecting duct → renal pelvis
Nephron
[in] = into blood vessel, [out]= from blood vessel
Glomerulus: [out] solutes, h2o, urea, creatinine
Juxtaglomerular apparatus: regulation of fil. rate & BP
PCT: [in] filtered h2o & solutes
Loop of Henle: maintain hypertonicity by countercurrent exchange
Thick ascending limb: [in] Na+, K+, Cl-, impermeable to h2o
Connecting segment: regulation of acid, HCO3-, Ca2+, Na+, K+
DCT: [in] Na+, Cl-, cations
CD: Regulation of acid, HCO3-, Na+, K+
Glomerulus filters the blood
network of capillaries
retain cellular component & medium to high-molecular-weight proteins
Structure of glomerulus: efficient, selective filtration
fenestrated capillaries
Bowman's space: collection of glomerular filtrate
Determined by mean net pressure, permeability, area available
Forces favoring filtration:
hydrostatic pressure of blood within capillary
oncotic pressure of fluid within Bowman's space
Forces opposing filtration:
plasma oncotic pressure within glomerular capillary
hydrostatic pressure in Bowman's space
increased plasma oncotic pressure, decreased hydrostatic pressure → decreased net filtration pressure
permeability of filtration barrier → structural & chemical characteristic of glomerular capillary wall
Filtration barrier: selective permeable
size
smaller > bigger
net electrical charge
cation > anion > neutral
Regulated by
Systemic
systemic blood pressure
intravascular volume
renin-angiotensin-aldosterone system
Intrinsic
renal blood flow *(cnghm pg532)
glomerular capillary pressure
myogenic reflex
tubuloglomerular feedback
Measured by determining the plasma clearance rate of a substance
rate of clearance: rate of elimination of substance divided by its plasma concentration
using inulin
endogenous creatinine clearance